DESCRIPTION: (Verbatim from application) This research will coordinate sonomicrometry, electromyography, and digital videography to examine how muscle function is modulated to perform motor behaviors with contrasting mechanical requirements. To achieve this objective, this study will extend current electromyographic analyses of limb muscle function in freshwater turtles to correlate hindlimb kinematics with hindlimb muscle length changes (strain), as well as activity patterns (EMG), during swimming and walking in turtle species that possess different degrees of specialization for aquatic locomotion. Freshwater turtles are an excellent model system for examining the modulation of muscle function, first because all species use their limb muscles for two types of locomotion (swimming and walking) with very different functional requirements, but also because some species use one form of locomotion infrequently, allowing modulation to be examined between behaviors that differ in frequency of use. Specific research aims include (1) evaluating correlations between changes in muscle strain and activity across behaviors, and (2) evaluating trends in the modulation of muscular strain patterns across behaviors used with different frequencies. By taking advantage of natural variations in behavior among turtle species, this study will provide insight into general patterns in the changes in muscle function required to allow the same morphological structure to be used to perform multiple tasks.